Sail crossover is a term used to refer to a boat’s combination of sails for all conditions. Each sail has a range of use, beyond which a smaller sail will replace it. The points where the first sail needs to be replaced for the second indicate sail changes. The crossover diagram shows us the overlap points between the sails and the appropriate moments for sail changes. At the crossover point of the sails we will have situations where two alternative sail combinations are valid. Changes must be made if we expect conditions to vary in favor of one combination or the other.
The wider the point of overlap between the sails, the more our sails suit is wide and flexible. If, on the other hand, the overlaps are very limited, it means that when the angle or intensity of the wind varies we are called to frequent sail changes. In fact, as soon as we leave the ideal range of use of a sail, with a limited overlap compared to the next sail, we have to make a sail change.
Using an out-of-range sail is not something to aim for, but there are variable weather situations where reducing the number of sails changes becomes an advantage. In fact, when we have clear all the possible combinations of sails for our boat, we must also have clear the times required for the manoeuvres. Some sail changes may require you to without a headsail until the new sail is hoisted. If our changes become very frequent, we unnecessarily waste time and energy.
The range of use of the sails
By range of use of the sails we mean the minimum and maximum wind and angle for which a sail is efficient. When we are out of these parameters we are called to sail changes. It may not be a question of sail changes but of canvas reductions. The mainsail reefs are the most obvious example, but there are other sails that can be reefed or reduced in area. On the Mini 650, for example, the solent usually has two reefs. Even the large spinnaker can often be reduced to a medium spinnaker thanks to a zip. On the Class40 the staysail may have a reef point.
On cruising boats it is also possible to furl the genoa and use it partially furled. In case performance is not our priority it is a very convenient thing. The sail usually has small circles that indicate three levels of reduction, as for reefs. Some cruise boats, especially in the Mediterranean, do not even have the possibility to hoist a staysail. Worse still, many cruising boats have no realistic way of hoisting a storm jib.
This is really unacceptable, but the problem is that the boats leave yard without the possibility of rigging an internal forestay. Nowadays it is possible to make a textile forestay (Dyneema) that can be put to rest when we do not need to use the staysail. The sail can be left hooked or removed from the deck depending on the navigation. The storm jib can be hoisted immediately above the lowered staysail. This solution is found on racing boats and cruising boats prepared for the high seas.
Extend the range of use of a sail
The experienced sailor is also able to play around the range of use and reduce sail changes. For example if we are slightly under-canvassed we can temporarily sail higher. This allows us to postpone the manoeuvres until it is decided that conditions have stabilised. This situation typically occurs after a cold front, when the wind starts to drop but is still very gusty. In this situation we are forced to remain cautious or otherwise suddenly find ourselves with the wrong sails and do damage.
The same is true when the wind increases, if for example a cloud or a gust leads to a greater wind for a short time. If we do not believe this is a permanent wind change, we must avoid unnecessary sail changes. If we are upwind, for example, we can sail through the gusts by depowering the mainsail. To do this we can act on the mainsail track and twist of the sail. To use mainsail track is certainly a practice that many are used to.
Temporarily de-powering the top of the mainsail by increasing its twist is another technique. This makes the sail less efficient upwind but makes it more forgiving, and therefore may not be wrong with waves. If, on the other hand, the situation is not temporary but lasting then it is better to reef and have a flat and efficient sail. For downwind sails, bearing away is the way to reduce apparent wind. By doing this we increase the range by temporarily avoiding a sail change.
The sail changes table
On every respectable boat (racing but not only) there should be a sail change table. This is in fact the tabular form of the sail crossover graph. For every 5-10 degrees of wind angle and 2 knots of wind intensity we will indicate the optimal sails combination. Those who know their boat well have this table well engraved in their mind. However, having it printed helps a lot in making choices when we are tired. How many times have we asked ourselves if the big masthead the right choice for such angle and strength of wind? This is because our historical memory did not come to our aid.
With a table of sail changes the answer is at hand and avoids unnecessary navigation with inefficient combinations. Indeed, the skipper must always and continuously ask himself if the current combination is the right one. Obviously he will have to worry not only about the immediate tactics but also about the overall strategy. If the tactic is an almost instantaneous factor, the strategy is the set of tactical choices over time. Thus the tactician’s mind could call for manoeuvres that the strategist’s mind will anticipate or postpone. This is based on weather forecasts, positioning with respect to the fleet and more.
That said, creating an accurate sail change table is very important. The table must be realistic about your actual abilities and what you would actually do. At the Global Ocean Race we started with the table that indicated that the large spinnaker to be taken down in 22 knots of true wind speed. That reflected thickness of our skin upon departure. At the end of the race the real figure was around 30 knots as we rarely took it down earlier. Our skin had thickened. The small spinnaker, the code 5, has seen 45-50 knots of wind, not without the right amount of apprehension.
Schedule the sail changes
It is clear that the manoeuvres must not be a surprise when they come. If we have our chart printed and posted in the cockpit and we have done our homework with respect to the weather, we have no excuse. Indeed, we can use the information to anticipate sail changes and always navigate within our limits. In fact, delaying a sail change only makes sense if we are managing a temporary gust. But if conditions are deteriorating, anticipating or being ready is the only right choice.
Scheduling the sail changes also means having time to discuss the manoeuvres with the crew. If you are sailing alone, prepare everything without rush and in safety. With everything under control you avoid problems and hitches, mistakes can waste a lot of time. By taking out the sails bags in time we have to make sure they are well secured on deck before the sails change. Losing a sail out to sea is a much more common mistake than you might imagine.
Obviously the manoeuvres depend a lot from boat to boat. For those who race around the cans they certainly don’t have furling genoas with reef marks. Indeed, there are several headsails and the even if there is a further there ovten two grooves to perform a sail change. For offshore boats, the sails can be hoisted furled, like staysails with a halyard lock, or hanked on removable inner forestays. Downwind sails can be prepared with woolen thread, hoisted, or on small boats hoisted from a bag.
Sail changes on a Mini 650
To give some practical examples, let’s consider a Mini 650. The sail suit of these boats has 7 sails in total trisail as an optional eighth sail. Let’s see what these 7 are including any reefs.
- Mainsail (3 reefs)
- Jib (1 reef)
- Storm Jib (1 reef)
- Large spinnaker (with possible reduction zip)
- Medium spinnaker
- Code 5 (Small Spinnaker)
- Code zero / gennaker
- Trisail (optional)
As you can see, the sails are few but the combinations are by no means few. Upwind the first and second reefs will progressively be taken. At that point a first reduction will be given to the jib, then a third reef to the main is taken and finally the second reef to the headsail. When even this canvas is excessive it will be time to change down to the storm jib. On some Mini 650s this is rigged on the inner stay, on others on the forestay after above the lowered headsail. Reefing headsails at the bow is uncomfortable and you get wet easily. Anticipating these manoeuvres allows you not to work in extreme condit